I've been doing fine specially on pavement and concrete, already finished a few 5K and 10K finally after 10 months of having get rid of shoes. I exclusively run barefoot and my soles and whole body had been adapting pretty well so far. Since I've been increasing my strengt and running workouts I decided to try a new one from an article a found. The guy who is inspiring by the way, does a workout which combines weight lifting (4 or 5 ) sets and run 1.25 miles on the treadmill between sets. I was feeling great but 15 minutes after finished it I noticed a bruise on my ankle and some tenderness in my tendon and on the left foot like if I was stepping on a stone on my forefoot. Nothing major and my PT treated me so i was great. But then I tried just 2 miles on the street as I always do and that bruise that has gone practically the next day came back and I felt some pain. From 0 to 10 let's say 3. My question is if the treadmill could be the problem. I never use it. I only run on hard surfaces or natural trails. Thank you in advance for any suggestions.